Abstract:

In one aspect of the method for displaying an image on a screen of a
cockpit of an aircraft, control means: control a first display on the
screen of an image comprising a background; and then control a second
display so that, in at least one zone of the image that is determined
independently of the background, the background presents a non-zero
second mean luminance that is less than a first mean luminance that it
presented during the first display.
In another aspect, the control means control the display on the screen of
an image comprising a background in such a manner, that at least in a
zone of the image that is determined independently of the background, the
background presents non-zero mean luminance that is less than mean
luminance of the remainder of the background.

Claims:

1. A method of displaying an image on a screen in a cockpit of an
aircraft, wherein control means:control a first display on the screen of
an image comprising a background; and thencontrol a second display so
that, in at least one zone of the image that is determined independently
of the background, the background presents a non-zero second mean
luminance that is less than a first mean luminance that it presented
during the first display.

2. A method according to the preceding claim, wherein at least in the
zone, the display means control the display of at least one sign that is
distinct from the background.

3. A method according to claim 1, wherein the control means leave switched
off at least one predetermined pixel of a pattern in each occurrence of
the pattern that is repeated to form the background at least throughout
the zone.

4. A method according to the preceding claim, wherein the pattern
comprises four pixels arranged in a square, and the control means cause
two pixels situated in two opposite corners of the square to be left
switched off.

5. A device for controlling the display of an image on a screen of a
cockpit of an aircraft, wherein the device is suitable for:controlling a
first display on the screen of an image comprising a background; and
thencontrolling a second display so that, in at least one zone of the
image that is determined independently of the background, the background
presents a non-zero second mean luminance that is less than a first mean
luminance that it presented during the first display.

6. A device according to the preceding claim, including at least one
graphic memory having the following graphics layers:a layer forming the
background of the image;an intermediate layer suitable for attenuating
the mean luminance of the background at least in the zone; anda layer
forming at least one sign.

7. A method of displaying an image on a screen of a cockpit of an
aircraft, wherein the control means control the display on the screen of
an image comprising a background in such a manner, that at least in a
zone of the image that is determined independently of the background, the
background presents non-zero mean luminance that is less than mean
luminance of the remainder of the background.

8. A device for controlling the display of an image on a screen of a
cockpit of an aircraft, wherein the device is suitable for controlling
the display on the screen of an image comprising a background in such a
manner, that at least in a zone of the image that is determined
independently of the background, the background presents non-zero mean
luminance that is less than mean luminance of the remainder of the
background.

9. An image displayed on a screen of a cockpit of an aircraft, wherein the
image comprises a background and presents at least one zone that is
determined independently from the background, in which the background has
non-zero mean luminance that is less than mean luminance of the remainder
of the background.

10. A computer program, including code instructions suitable for
controlling the execution of a method according to claim 1 when executed
by a computer.

11. A computer program, including code instructions suitable for
controlling the execution of a method according to claim 7 when executed
by a computer.

Description:

[0001]The invention relates to aircraft, and in particular to displaying
images and data on a screen of an aircraft cockpit.

BACKGROUND OF THE INVENTION

[0002]It is known to provide multifunction liquid crystal screens in the
visual display systems of aircraft cockpits, where such screens are
capable of displaying a large amount of information simultaneously. The
information may have a variety of presentations: [0003]text and simple
crosshairs generated by the display unit; [0004]a bitmap type colored
background provided by a system external to the visual display system;
and [0005]a complex video image also provided by an external system.

[0006]In order to optimize graphics processing and to guarantee correct
priority levels for the symbology generated by the visual display system,
it is known that the graphics memory that defines the content of the
digital image for display on the matrix of the screen may be organized as
a plurality of graphics planes, specifically: [0007]a symbology plane;
[0008]a matrix or bitmap plane; and [0009]a video plane.

[0010]Under such circumstances, it is possible to display on the screen an
image that presents a background of strong graphic density having signs
associated with some particular symbology superposed thereon. By way of
example, the background may be a map, a radar image, information provided
by a database relating to terrain, or indeed a satellite image. The
function of the background is to improve the aircraft pilot's perception
of the surroundings outside the aircraft. Nevertheless, it does not
constitute primary means for guaranteeing flight integrity.

[0011]The symbology may be associated with information relating to a
variety of domains such as the flight plan, radio-navigation, managing
on-board systems, sending messages or alarms, or indeed elements
concerning monitoring the surrounding air space. Such elements may for
example relate to traffic alert and collision avoidance systems (TCAS).

[0012]This information is generally more critical than the background
image, and in any event of higher priority for flight integrity. That is
why the way in which the graphics planes are organized ensures that the
symbology is always drawn so as to be visible in front of the background
image, i.e. on top of it.

[0013]Nevertheless, that does not suffice to ensure that the symbology is
clearly legible under all circumstances, in particular if the background
is moving or cluttered with numerous graphics elements of different
colors.

[0014]Unlike raster-scanning cathode ray screens where superposing signs
has the result of increasing the light intensity of each pixel, thereby
ensuring satisfactory contrast in all circumstances, with matrix type
screens such as liquid crystal screens, such superposition involves a
priority order. Thus, at each pixel of the image, only the element
corresponding to the graphics plane having the highest priority is
displayed. In other words, only the color (and consequently the
luminance) of the sign having the highest priority is displayed amongst
signs that are superposed.

[0015]Under such conditions, since liquid crystal screens are nowadays
greatly preferred over raster-scanning cathode ray screens, it is
important to make priority information clearly visible on the image.

[0016]One known solution for improving the legibility of the symbology on
the background is haloing. That consists in emphasizing the outline of
the priority item (e.g. a character or crosshairs) by a black line that
artificially increases the contrast between the item and the background
that surrounds it. Nevertheless, that technique is effective above all
when the signs are on a colored background that is relatively uniform or
when the sign forms solid crosshairs. It is found to be much less
effective with characters, or thin traces that are displayed on a
background presenting high resolution.

OBJECT AND SUMMARY OF THE INVENTION

[0017]An object of the invention is thus to improve the display of
important information on an aircraft screen that takes priority of items
of information into account relative to one another.

[0018]For this purpose, the invention provides a method of displaying an
image on a screen of an aircraft cockpit, in which control means:
[0019]control a first display on the screen of an image comprising a
background; and then [0020]control a second display so that, in at least
one zone of the image that is determined independently of the background,
the background presents a non-zero second mean luminance that is less
than a first mean luminance that it presented during the first display.

[0021]The change in luminance prepares the image and the observer for
displaying a sign in the zone under consideration. The sign may also be
displayed during the second display step, at the same time as the second
mean luminance appears. Thus, in the zone, it is possible to display a
sign independently of the background so that the sign stands out from the
background with good contrast to ensure good legibility. For example, in
certain zones of the screen, the invention may amount to interposing an
intermediate layer between the background graphics plane and the graphics
plane for signs that are distinct from the background, which intermediate
layer is semi-transparent, attenuating the luminance of the background in
the zone. Its purpose is to attenuate the mean luminance of the
background so as to improve the contrast of the sign present in the zone,
while nevertheless ensuring a certain amount of legibility for the
background in that zone. The image thus appears as though it has a
background, but with data that is visible in front of the background and
a semi-transparent intermediate veil or layer interposed between the data
and the background.

[0022]It should be observed that the method may be implemented in such a
manner that the control means: [0023]control the display of the image
in such a manner that throughout the image the background presents the
first mean luminance; and then [0024]control the display of the image in
such a manner that, once more throughout the image, the background
presents a non-zero second mean luminance that is less than the first
luminance.

[0025]This corresponds to a situation in which the entire background image
is shaded.

[0026]Advantageously, at least in the zone, the display means control the
display of at least one sign that is distinct from the background,
preferably in such a manner as to present mean luminance that is greater
than the second luminance, at least in the zone.

[0027]Advantageously, the display means control the display of the sign so
that it presents mean luminance greater than a mean luminance of another
sign in the zone and distinct from the background.

[0028]Thus, the image appears as though the semi-transparent layer also
covers some of the signs of the zone but not all of them. This may serve
to make certain signs visible and legible to a greater or lesser extent
in order to reveal a priority order amongst them.

[0029]Advantageously, the control means control the display of the sign in
such a manner that it presents mean luminance less than mean luminance of
another sign of the image lying outside the zone.

[0030]In an embodiment, the control means leave switched off at least one
predetermined pixel of a pattern in each occurrence of the pattern that
is repeated to form the background at least throughout the zone.

[0031]Thus, the graphics processing of the zone for displaying the
background is reduced to a minimum and makes use of few computer
resources. This method enables the luminance of the zone in question to
be reduced very simply, thereby increasing the contrast of the symbology
overlying the background in said zone. It does not introduce any
colorimetric distortion. If the background is absent from the image, then
the pattern as such does not appear. Finally, this method enables
resolution to be obtained that is sufficiently fine not to disturb
reading of the image.

[0032]Preferably, the control means preferably leave switched off at least
two pixels of the pattern.

[0033]Also preferably, the pattern comprises four pixels arranged in a
square, and the control means cause two pixels situated in two opposite
corners of the square to be left switched off.

[0034]In an embodiment, the zone does not include any sign in addition to
the background.

[0035]Advantageously, the or each zone lies at the periphery and/or at the
center of the image.

[0036]Advantageously, the background occupies the major fraction of the
surface area of the image.

[0037]Preferably, the background extends to each edge of the image.

[0038]Advantageously, the screen is a matrix screen.

[0039]The invention also provides a device for controlling the display of
an image on a screen in an aircraft cockpit, the device being suitable
for: [0040]controlling a first display on the screen of an image
comprising a background; and then [0041]controlling a second display so
that, in at least one zone of the image that is determined independently
of the background, the background presents a non-zero second mean
luminance that is less than a first mean luminance that it presented
during the first display.

[0042]Preferably, the device comprises at least one graphic memory having
the following graphics layers: [0043]a layer forming the background of
the image; [0044]an intermediate layer suitable for attenuating the mean
luminance of the background at least in the zone; and [0045]a layer
forming at least one sign.

[0046]The invention also provides a method of displaying an image on a
screen of a cockpit of an aircraft, wherein the control means control the
display on the screen of an image comprising a background in such a
manner, that at least in a zone of the image that is determined
independently of the background, the background presents non-zero mean
luminance that is less than mean luminance of the remainder of the
background.

[0047]Thus, whereas in the first aspect of the invention, the luminance of
at least one point is varied in time by comparing two steps of displaying
the image or two representations of the image, here the distinction is
made in space by distinguishing one zone of the background from the
remainder of the background. Once more, good contrast is obtained between
the sign and the background visible behind it in the zone in a manner
that is simple.

[0048]The invention also provides a device for controlling the display of
an image on a screen of an aircraft cockpit, the device being suitable
for controlling the display on the screen of an image comprising a
background in such a manner, that at least in a zone of the image that is
determined independently of the background, the background presents
non-zero mean luminance that is less than mean luminance of the remainder
of the background.

[0049]The invention also provides an image displayed on a screen of an
aircraft cockpit, the image comprising a background and presenting at
least one zone that is determined independently from the background, in
which the background has non-zero mean luminance that is less than mean
luminance of the remainder of the background.

[0050]The image also provides a signal for an aircraft cockpit, the signal
representing an image of the invention and being suitable for causing it
to be displayed on a screen of the cockpit of the aircraft.

[0051]Finally, the invention provides a computer program including code
instructions suitable for controlling the execution of a method according
to either of the aspects of the invention when it is executed on a
computer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0052]Other characteristics and advantages of the invention appear further
from the following description of an embodiment given by way of
non-limiting example and with reference to the accompanying drawings, in
which:

[0053]FIG. 1 is a perspective view of an airplane having the invention
implemented on board;

[0054]FIG. 2 is a diagram of a device of the invention as present on board
the FIG. 1 airplane;

[0056]FIG. 4 is a view analogous to FIG. 3, showing the detail of an
image; and

[0057]FIG. 5 shows an example of an image displayed by the screen of the
FIG. 2 device.

MORE DETAILED DESCRIPTION

[0058]FIG. 1 shows an aircraft 2 having the method of the invention
implemented on board. The aircraft shown is specifically an aerodyne,
here an airplane comprising a fuselage 4, two wings 6, two engines 8
carried by respective ones of the wings, and a tail 10. At the front of
the fuselage, the airplane has a cockpit 12 occupied by one or more
pilots.

[0059]The cockpit includes one or more (visual) display systems. The
description below relates to one such display system 14. The system
comprises a computer 16 and a screen 18 connected to the computer.
Specifically the screen is a matrix screen, e.g. a liquid crystal screen.
Unlike the screen 18, it is entirely possible for the computer 16 to be
located outside the cockpit.

[0060]The system 14 is connected by on-board telecommunications means 20
to other on-board systems 22, 24, and 26, each including at least one
computer. These systems 22 to 26 may relate to functions as varied as
mapping, radar imaging, a terrain database, satellite imaging, the flight
plan, radio-navigation, managing on-board systems, managing messages and
alarms, or indeed monitoring the surrounding air space.

[0061]The computer 16 includes one or more memories and at least one
microprocessor. The function of the system 14 is to deliver an image 30
on the screen 18 to provide the pilot with data and/or information
relating to the flight, to the aircraft, and to its surroundings. The
image in this example is of rectangular shape so that it has four
rectilinear edges, respectively top, bottom, left, and right edges. The
computer 16 forms control means suitable for controlling the
implementation of the steps of the method of the invention as described
below. These means serve in particular to cause the image 30 to be
displayed on the screen 18.

[0062]The image 30 includes a background 32. By way of example, the
background may be a map, a radar image, a representation of terrain taken
from a database, or indeed a satellite image. It may be a video image.
The background extends to each of the four edges of the image 30. The
background forms the portion of the image that gives the impression of
being visible behind the image.

[0063]The image comprises signs that are distinct from the background and
that appear to be in front of it, i.e. above it. The background is
contiguous with the signs. In FIG. 2, there can thus be seen signs 34
reading "data 1", 36 "data 2", and 46 "data 3". These signs may generally
be constituted by letters, words, symbols, or indeed drawings or marker
lines. In spite of the presence of these signs, the background occupies
the major fraction of the total area of the image.

[0064]The computer 16 determines one or more zones 38, 40, 42, and 48 on
the image 30. These zones are determined independently of the background,
i.e. independently of the information content of the background. This
determination may be identical under all circumstances. Alternatively, it
may be adapted as a function of circumstances. The zones 38 to 40 occupy
the bottom left and right corners of the image. The zone 42 forms a top
strip. The zone 48 extends in the central portion of the image. The zones
are rectangular in shape in this example.

[0065]The signs 34 "data 1" and 46 "data 3" lie in the zone 38. The sign
36 "data 2" lies outside the above-mentioned zones. The zones 40, 42, and
48 do not include any signs in addition to the background.

[0066]In each of these zones, the control means 16 cause the display to
operate in such a manner that the background 32 presents non-zero mean
luminance that is less than the mean luminance of the remainder of the
background. Specifically, the remainder of the background is constituted
by all portions of the image with the exception of the signs 34, 36, and
46, and of the zones 38, 40, 42, and 48.

[0067]Specifically, the luminance difference is implemented as follows.
FIG. 2 shows a detail C as visible on the screen, but to a larger scale,
and FIG. 3 shows an enlargement of a detail D of the detail C. Since the
image 30 is a matrix image, it is formed of elements 44 known as pixels,
that are arranged in an array and that form a table of rows and columns.
Each of the pixels may be activated to deliver light with a certain
luminance and a certain chrominance. Each of the pixels of the screen is
thus controlled individually to display a portion of the image.

[0068]In the zone 38, a pattern 50 is defined that repeats to form the
entire zone. Specifically, the pattern is a rectangular pattern that is
square as shown in FIG. 3. This pattern 50 comprises four adjacent pixels
arranged in a square. The entire zone 38 is thus represented by repeating
this pattern in the horizontal and vertical directions.

[0069]In the zone 38, in order to display the background 32, in each
occurrence of the pattern, at least one same predetermined pixel of the
pattern is left switched off, and in the example shown two predetermined
pixels 44a and 44d are left off, i.e. the top left and bottom right
pixels in the pattern, as shown in FIG. 3. The luminance of each of these
pixels is therefore zero and they appear black. Thus, in the zone 38,
only one pixel in two is switched on for displaying the background. The
other two pixels 44b and 44c receive luminance and chrominance commands
that are identical to those they would have received if the background
were being displayed normally in the absence of the zone 38. Given that
only one pixel in two is on in this example, the mean luminance of the
background in the zone 38 is divided by two compared with the mean
luminance in the portion of the background that lies outside the zones
38, 40, 42, and 48.

[0070]FIG. 4 thus shows the situation where it is desired to give the
background a yellow color in the detail C that covers a portion of the
zone 38 and a portion of the background that lies outside the zones 38,
40, 42, and 48. The pixels 44 that lie outside the zone 38 all receive a
chrominance command that corresponds to the yellow color and a normal
luminance command. In contrast, in the zone 38, only one pixel in two
receives such a command with the other pixels being kept off so that
their luminance is zero.

[0071]As can be seen in FIG. 2, in the present example, one of the signs,
the sign 34, lies in the zone 38 of the image, while another sign, the
sign 36, lies in a portion of the image that is not occupied by the
above-mentioned zones. The sign 34 is distinct from the background 32.
The control means cause the sign 34 to be displayed in such a manner as
to present mean luminance that is greater than the mean luminance of the
background in the zone 38 and identical to the mean luminance of the sign
36 that lies outside the zones 38, 40, 42, and 48. Specifically, the sign
34 "data 1" receives a normal display command and thus presents good
display contrast relative to the background of attenuated luminance in
the zone 38.

[0072]Different signs may be displayed in a given zone, and by way of
example the signs 34 "data 1" and 46 "data 3" are both displayed in the
zone 38. They can then be displayed in such a manner that they present
the same mean luminance, this mean luminance also being identical to the
mean luminance of the sign 36 that is situated outside the zones 38, 40,
42, and 48. Alternatively, the display may be controlled in such a manner
that the sign 46 presents, for example, mean luminance that is less than
the mean luminance of the sign 34 or of the sign 36. This may be done for
example merely by applying the same method using the above-mentioned
pattern, switching on only one pixel in two of the pixels associated with
the sign 46.

[0073]The control means 16 are arranged to generate a signal
representative of the image 30 in order to display it on the screen 18.
This signal passes via a cord 50 connecting the computer 16 to the
screen.

[0074]In another aspect of the invention, it may be considered that one of
the zones 38, 40, 42, and 48, e.g. the zone 38, is initially absent when
the image 30 is displayed for the first time on the screen 18. The
background 32 will therefore be displayed with attenuated mean luminance
only in the zones 40, 42, and 48, with the background in all other
locations being displayed normally with a first luminance, ignoring the
presence of the signs.

[0075]In a subsequent step, the control means 16 send a new version of the
image 30 to the screen 18, this new version having the zone 38. Under
such circumstances, in the new version of the image, the background
presents a second mean luminance that is less than the first luminance
that it previously presented at the same location in the image at the
preceding step prior to said zone appearing on the screen. In a third
step, the display of this zone may precede the display of the data, e.g.
the data 34 and 46 in the zone 38. Alternatively, it make take place
simultaneously with the appearance of said data in the zone. It is thus
possible either to provide for the intermediate transparent layers to be
displayed permanently, or else to constrain the presence thereof to the
presence of signs, e.g. texts that they are to show up.

[0076]To implement the method, the graphics memory of the computer 16 is
organized so that it has the following distinct superposed graphics
planes or layers: [0077]a layer forming the background 32 of the image;
[0078]an intermediate layer suitable for attenuating the mean luminance
of the background in the zones 38, 40, 42, and 48 by using the
above-mentioned pattern; and [0079]a layer that serves at least to form
the signs 34, 46.

[0080]The method of the invention may be implemented by means of a
computer program stored in the computer 16 and including lines of code
suitable for controlling the implementation of the steps of the method
when executed on a computer. The program may be recorded on a fixed or
removable data recording medium. Provision may be made for the program to
be made available on a telecommunications network for downloading.

[0081]The invention, which makes it possible to introduce a
semitransparent intermediate layer between the symbology and the
background of the image and serves here to manage the semi-transparency
by means of a specific raster pattern, thus provides a good compromise
between showing up priority information and the observer continuing to
perceive the elements of the image background. The invention is
compatible with extending the image and its background over the entire
screen. The invention makes it unnecessary to provide opaque masks that
are applied to the image in order to make the signs readable, which
opaque masks would serve to avoid the background of the image interfering
with the symbology, but would deprive the pilot of a portion of the
background. The invention thus serves to improve the pilot's perception
of the surroundings. The invention is very flexible in its
implementation. It is thus possible to choose freely the zone(s) of the
image that is/are concerned, the display conditions in such a zone, and
the color(s) associated with such a zone.

[0082]It can be understood that the invention also makes it possible to
provide different semi-transparent layers interposed between different
levels of symbology in order to increase discrimination and enhance the
observer's perception of priorities. Thus, three or more symbols in a
given zone may have mutually different mean luminances. For example, the
decreasing priority levels of different signs may be displayed with
patterns in which, respectively: [0083]none of the pixels 44 is off;
[0084]one in four of the pixels is off; [0085]two of the pixels are off;
and [0086]three of the pixels are off.

[0087]Preferably, only certain portions of the image implement the method
of the invention so as to reduce the additional graphics load the
invention generates in terms of image production.

[0088]FIG. 5 shows a detailed example of an image displayed using the
screen 18. A rectangular zone 38 situated in the top right corner of the
screen presents reduced luminance and provides a multicolor background
presenting a grayed or shaded terrain map on which the signs 34 "MARINA"
in green and the sign 46 "18:35" in white stand out in particular. The
image presents two other similar rectangular zones 40 and 42 situated
respectively in the bottom right corner and in the top left corner. Apart
from these three zones where the background luminance is reduced, in the
remainder of the image the background presents normal luminance. The
three zones and the remainder include signs that stand out from the
background by having luminance that is not reduced. Provision may be made
for a large top zone of the image to present luminance that is slightly
reduced and for two strip-forming zones, one at the top and one at the
bottom, to have even lower luminance. In a variant, it is possible to
provide an image with only the two zones of attenuated luminance forming
top and bottom strips.

[0089]The image may be in color or in black and white.

[0090]Naturally, numerous modifications may be made to the invention
without going beyond the ambit thereof.

[0091]Provision may be made, independently of the invention, to use a
method of displaying an image that includes signs, a background visible
behind the signs, and a semi-transparent layer covering part of the
background behind the signs.

[0092]Provision may be made to reduce the luminance of the background in
the zones 38, 40, 42, and 48 without implementing a pattern.

[0093]If a pattern is used for this purpose, it may be a pattern that is
different from that shown in FIG. 3. For example, provision may be made
for a pattern forming a 3×3 matrix in which only the pixels of one
diagonal are off or indeed in which only one pixel is off, or on the
contrary only the central pixel of the pattern is on. In a square pattern
such as that shown in FIG. 3, provision may be made for only the top left
pixel or the bottom right pixel to be switched on, for example.

[0094]Although the invention is particularly advantageous when it is
implemented by means of a matrix screen, it is not restricted to this
type of screen and it may be used on a raster-scan screen.